Construction of the replacement pipelines will start soon after.

Apache said most of the replacing line pipe is in Karratha while the valving and related fittings will arrive in early July.

The company has 140 people on Varanus working to re-establish partial production from the plant within the next few months.

Meanwhile, the national Offshore Petroleum Safety Authority said its investigations into the incident are technical and expected to take at least three months to complete.

The authority warned that speculation on the causes of the gas pipeline rupture and fire may compromise the investigation team's ability to complete its work.

The incident slashed Western Australia's gas supplies by about 30% and has forced miners and other industrial customers to seek alternative fuel sources or reduce output.

Federal Resources Minister Martin Ferguson said in a statement earlier this week that the gas disruption would likely result in a short-term cut to Australia's exports and lower economic growth than what might have been the case.